1. Field of the Invention
The present invention relates to a liquid applying apparatus and an ink jet printing apparatus, and specifically, to a liquid applying apparatus that applies a liquid to a medium for a predetermined purpose, for example, for starting the coagulation of pigments earlier when printing is carried out using inks composed of the pigments as color materials. In particular, the present invention relates to control of the amount of liquid applied to the medium.
2. Description of the Related Art
Known such applying apparatuses supply a liquid to be applied, to an applying member such as a roller, which then applies the supplied liquid to a medium. Among the apparatuses using such an applying member for application, a configuration that seals a part of the roller to which an application liquid is supplied or applied is described in Japanese Patent Laid-Open No. 08-58069. The applying mechanism described in Japanese Patent Laid-Open No. 08-58069 applies inks to a roller in a gravure printing apparatus which has a pattern for a printing plate formed on a surface thereof. This mechanism uses an ink chamber having two doctor blades arranged at corresponding vertical positions along a peripheral surface of the roller and extending in a longitudinal direction of the roller and elastic members provided at the respective sides of each of the two doctor blades. The chamber is contacted with the peripheral surface of the roller to form a liquid chamber between the ink chamber and the roller. Then, the roller is rotated to supply or apply the application liquid to the roller.
The configuration supplying the liquid to the roller while abutting the chamber holding the liquid against the roller has the advantage of, for example, being able to prevent the possible leakage of the liquid. In particular, for ink jet printing apparatuses such as printers which comprise an applying mechanism, the configuration makes it possible to provide a printer which can prevent the leakage of the application liquid caused by a change in the posture of the apparatus during transportation and which is thus applicable to transportation.
However, the liquid applying apparatus described in Japanese Patent Laid-Open No. 08-58069 is disadvantageous in that the amount of liquid applied to a medium is likely to vary among products. That is, in the applying mechanism disclosed in Japanese Patent Laid-Open No. 08-5806, the chamber holding the liquid abuts against the roller. As the roller rotates, the liquid is attached to the roller via the abutting portion, and is conveyed and transferred to the medium. Thus, a variation in the condition of the abutment between the chamber and the roller may vary the amount of liquid applied to the roller.
For example, a variation the surface roughness of the roller surface among individual rollers may vary the condition of the abutment between the chamber and roller and thus the amount of liquid attached to the roller and fed to the exterior of the chamber. This may finally vary the amount of liquid transferred (applied) to the medium.